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Catholic and Federal University of Pelotas, Brazil. hiramalmeidajr@hotmail.com

Abstract

Phytophotodermatitis is a common cutaneous phototoxic reaction produced by contact with a variety of plant substances, followed
by sunlight exposure. Phytophotodermatitis can simulate child abuse , impetigo, superficial lymphangitis, and larva migrans.
The most frequent presentation is hyperpigmentation of the dorsum of the hands, but there are other less common findings such
as blisters or lesions mimicking solar lentigines and melasma.

Phytophotodermatitis is a common cutaneous phototoxic reaction. Contact with plant-derived phototoxic substances (furanocoumarins
or psoralens) followed by sunlight exposure produces the clinical lesions [1, 2]. These phototoxic substances are found in various vegetable families (Umbilliferae, Moracea, Rutaceae, and Leguminous) [3, 4]. Exposure may occur during fruit and vegetable processing, hiking, jogging, or by the use of plant-derived medicines and
cosmetics [3, 4, 5, 6, 7, 8, 9].

Phytophotodermatitis cases are seen worldwide. In the city of Pelotas (South Brazil), after telephone contact with local dermatologists
during 2 consecutive summers, an incidence of 16 cases per 100,000 inhabitants per year was estimated. The most common cause
in Pelotas is the Tahiti lemon.

In a prior study we demonstrated in rats that only the peel juice and not the fruit juice of lemons is associated with phytophotodermatitis
[13], confirming a previous study in humans [14].

Figure 1

Figure 2

Figure 3

Figure 4

The most common feature of phytophotodermatitis is hyperpigmentation on the dorsum of the hands (Fig. 1). In more seriously
affected cases, erythema and blisters may appear in the acute phase (Fig. 2). In the experimental model, exposure-time dependent
epithelial degeneration and necrosis is demonstrated, which leads to the blister formation [13]. The hyperpigmentation may be in large areas (Fig. 1) or punctiform, simulating solar lentigines (Fig. 3). In such cases
it may be that small drops of the peel juice are sprayed onto the skin surface during fruit handling. Bizarre hyperpigmented
lesions may form depending on how the phototoxin drips over the skin surface (Fig. 4).

Figure 5

Figure 6

Figure 7

The dorsum of the hands are often the most common sites of both chemical exposure and sun exposure and hence are most frequently
affected (Figs. 1 and 3), but sometimes the condition can appear differently. Some patients accidentally have contact with
the plant materials on other body parts; some hours later they may notice the sudden appearance of a "burned" area (Fig. 5).
During fruit or vegetable processing, contact may occur on the thighs (Fig. 6). A less common presentation of phytophotodermatitis
is seen on the upper lip, when the psoralens reach the skin when the patient drinks the peel juice or bites the fruit (Fig.
7); this form may mimic melasma. In the cases shown, the plant phototoxins were from the Tahiti lemon.

Generalists and patients often do not suspect contact phototoxicity as the cause of such strange hyperpigmented lesions and
blisters on sun-exposed skin. Patients must be instructed to handle with care vegetables that may induce phytophotodermatitis.
Concubinal cases have been reported and small children have been affected through the contaminated hands of babysitters.